Acute molybdenum toxicity to rainbow trout and other fish

Abstract

Molybdenum is generally reported in the literature to be acutely lethal to various fish species at relatively high concentrations (70 to >2000 mg/L). The toxicity of molybdenum to fertilized rainbow trout eggs and alevins (EA), however, is controversial as different bioassays demonstrate a wide toxicity range (0.73 to >90 mg/L Mo). A duplication of a previous study using similar water chemistry along with the standard bioassay protocol demonstrated that molybdenum was not acutely toxic to the early life stages of rainbow trout over 32 d up to a maximum molybdenum concentration of 400 mg/L. An additional bioassay exposing early life stages of rainbow trout to a maximum molybdenum concentration of 1500 mg/L for 32 d did not cause sufficient mortality to allow an LC50 to be calculated. Key words: molybdenum, toxicity, bioassays, rainbow trout.